IR: do not change overrides for lazy IR in FakeOverrideRebuilder

`FakeOverrideBuilder.provideFakeOverrides` recursively changes overrides
for all superclasses in the hierarchy, including lazy IR, which is a lot
of extra work.

Also it leads to some tests failing in the IR fake override builder mode
because it changes correct fake overrides of Java classes to incorrect
ones. Those tests are unmuted but it doesn't mean they are fixed -- most
likely we'll generate fake overrides via IR for lazy IR too, at which
point they'll start to fail again.

compiler/testData/codegen/box/javaInterop/conflictingOverloadsForThrowableInheritors.kt

@@ -1,5 +1,4 @@
 // TARGET_BACKEND: JVM
-// IGNORE_CODEGEN_WITH_IR_FAKE_OVERRIDE_GENERATION: KT-61805
 // FULL_JDK
 // ISSUE: KT-45584
 

compiler/testData/codegen/box/javaInterop/conflictingOverloadsForThrowableInheritors2.kt

@@ -1,6 +1,5 @@
 // TARGET_BACKEND: JVM
 // FULL_JDK
-// IGNORE_CODEGEN_WITH_IR_FAKE_OVERRIDE_GENERATION: KT-61805
 // ISSUE: KT-45584
 
 // FILE: PlaceholderExceptionSupport.java